Technical Field
The present disclosure relates to a surgical forceps, and more particularly, to a surgical forceps and method for determining and applying a minimum seal pressure to tissue based upon tissue diameter and/or composition.
Background of Related Art
As an alternative to open forceps for use with open surgical procedures, modern surgeons use endoscopic or laparoscopic instruments for remotely accessing organs through smaller, puncture-like incisions. More recently, Natural Orifice Translumenal Endoscopic Surgery (NOTES) procedures have been developed, for example, to access the abdominal cavity via the mouth, for scar-less surgery. Much like laparoscopy, NOTES is beneficial to patients in that it reduces healing time. However, while these minimally invasive surgical procedures are advantageous in many respects, the reduced access area presents new problems for surgical instrument design. For example, achieving a high seal pressure with a surgical forceps becomes increasingly more difficult as the size of the jaw members decreases. Accordingly, determining a minimum seal pressure needed to effectively seal tissue having a given diameter would be helpful in designing surgical instrument for use in laparoscopic or NOTES procedures.
Further, the proper seal pressures, or seal pressure ranges, required to effectively seal vessels of particular diameters is also important. Accurate application of pressure is important to oppose the walls of the vessel, to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue, to overcome the forces of expansion during tissue heating, and to contribute to the end tissue thickness which is an indication of a good seal. If the pressure is not great enough, the vessel may not properly or effectively seal and if the pressure is too great, the seal may shred or tear. It has been found that the amount of force required to produce an effective seal is at least partly dependent on the size and composition of the tissue to be sealed. Therefore, in order to help ensure an adequate seal, it would be advantageous to initially determine the size and/or composition of the tissue to be sealed and then apply the appropriate seal pressure.
Accordingly, a study was conducted to determine how seal pressure and blood vessel size influence the quality of the seal produced, measured through burst pressure. Seal pressure refers to the force imparted to tissue disposed, for example, between opposing jaw members of a surgical forceps. Burst pressure is the pressure required to open, or burst, a previously sealed vessel by forcing a fluid through the sealed vessel. The study was designed using a central composite response surface, a well known Design of Experiments (DoE) variation. The DoE contained two factors: seal pressure and vessel size. The range of values tested for seal pressure was 40 psi to 120 psi, while the vessel diameters ranged from 2 mm to 6 mm.
In testing, porcine renal arteries were removed and dissected and the diameter of the vessel was measured. The vessel was then placed on a research tool used for electrothermal bipolar vessel sealing. The pressure between the jaw members was set on the research tool to correspond with the appropriate seal pressure dictated by the DoE. A vessel seal was produced by applying bipolar energy to the seal plates using a ForceTriad™ generator manufactured by Valleylab (now Covidien Energy-based Devices) of Boulder, Colo. Once the seal was made, the vessel was held in place while water was pumped through the vessel for burst testing. A pressure calibrator was used to determine the maximum pressure the vessel could withstand prior to bursting. The burst pressures for all of the vessel sizes and pressure combinations were input into a statistical software package for further analysis. An Analysis of Variation (ANOVA) evaluation revealed that both vessel size and seal pressure were significant factors in determining the burst pressure (quality) of the resultant seal.